Optimism and pessimism in strategic interactions under ignorance

We study players interacting under the veil of ignorance, who have -- coarse beliefs represented as subsets opponents' actions. analyze when these follow $\max \min$ or $\max\max$ decision criteria, which we identify with pessimistic optimistic attitudes, respectively. Explicitly formalizing attitudes and how reason interactively characterize behavioral implications related to common belief in events: while optimism is Point Rationalizability, a new algorithm Wald Rationalizability captures pessimism. Our characterizations allow us uncover novel results: ($i$) regarding optimism, relate it wishful thinking \'a la Yildiz (2007) prove that dropping (implicit) "belief-implies-truth" assumption reverses an existence failure described therein; ($ii$) shed light on notion rationality ordinal games; ($iii$) clarify conceptual underpinnings behind discontinuity hinted analysis Weinstein (2016).